Low-dimensional transition metal chalcogenides for electronics applications
Bloodgood, Matthew Abbott
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The chemistry and structure of low-dimensional materials are an important consideration for nanoscale, electronics applications. The oxidative chemistry of 2-dimensional 1T-TiSe2 and 1T-TaSe2 is explored in chapter II. Oxidation onset temperature, oxide layer thickness, and polymorph transitions associated with prolonged, ambient storage are discussed. The oxidative stability of 1T-TiSe2 was found to be lower than that of 1T-TaSe2 with each material reaching full oxidation at 400 and 600 °C after 1 h, respectively. A phase transition in TaSe2 after prolonged storage in ambient conditions inspired further study of polymorphism. Investigation of the polymorphic, transitional pathways of 1T-TaSe2 in chapter III revealed two previously unreported transitions. The first is a transition to the room temperature stable phase from 3R to 2H-TaSe2, followed by a transition to the metastable 4H(x) polymorphs (x = a or c). Polymorphism investigation is continued with the study of the NbS3 system described in chapter IV. Two newly established polymorphs of NbS3, along with high-resolution characterization, are reported. These studies are integral advances in knowledge for the advancement of nanoscale electronics.